Chromosomal abnormalities cause a wide range of disorders associated with birth defects and intellectual disability. Many of these disorders can be diagnosed prenatally by analysis of chorionic villi or amniocytes.
Chromosomal microarray (CMA) is a high-resolution method and is sometimes called a molecular karyotype.
The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine recommend CMA as a replacement for the fetal karyotype in patients with a pregnancy demonstrating 1 or more major structural abnormalities on ultrasound when undergoing invasive prenatal diagnosis. Also, patients requesting invasive diagnostic testing should be offered prenatal CMA.
How to Use This Test:
Common reasons for performing chromosomal microarray (CMA) for prenatal diagnosis include:
Copy number variation is found in all individuals, including patients with abnormal phenotypes and normal populations. Therefore, determining the clinical significance of a rare or novel copy number change can be challenging. Parental testing may be necessary to further assess the potential pathogenicity of a copy number change.
Identification of regions of excessive homozygosity on a single chromosome could suggest uniparental disomy, which may warrant further clinical investigation when observed on chromosomes with known imprinting disorders.
The detection of excessive homozygosity on multiple chromosomes may suggest consanguinity.
CMA does not detect balanced chromosome rearrangements such as Robertsonian or other reciprocal translocations, inversions, or balanced insertions.
Point mutations, small deletions, or insertions below the resolution of the array are also not detected.
Chromosomal Microarray (CMA) using Affymetrix Cytoscan HD
Varies: Chorionic Villi or Amniotic Fluid
Day(s) and Time(s) Test Performed:
Samples processed Monday through Sunday.
Alyssa Frank is a Marketing Segment Manager at Mayo Clinic Laboratories. She leads marketing strategies for product management and specialty testing. Alyssa has worked at Mayo Clinic since 2015.